Abstract: When a tunnel boring machine(TBM) tunnels through fault fracture zones in the Tianshan Shengli tunnel on the UrumqiYuli expressway, severe loosening and falling of surrounding rocks occur. Therefore, numerical simulation methods are employed to examine the deformation and plastic zones of the surrounding rock using traditional and steeltube support methods, investigating the support effect of steel tubes. Additionally, a field investigation is conducted to comparatively analyze the construction efficiency and economy of various support methods, illustrating the applicable conditions for each. The results reveal the following: (1) In the fault and fracture zones, the deformation and plastic zone of the surrounding rock increase after the TBM shield passes through, aggravating the damage of surrounding rock. The traditional support method with bolts and steel arches cannot effectively control the deformation of surrounding rock and plastic zone development. (2) The cumulative settlement of surrounding rock supported by steel tubes is 53% lower than that with traditional support methods in fault and fracture zones, with faster convergence of the surrounding rock deformation, showing a good control effect on deformation and plastic zone development of surrounding rock. (3) The plastic zone of the surrounding rock supported by steel tubes is smaller than that of traditional support methods, with a 44% reduction in sidewall, showing that the steel tube support method benefits the surrounding rock stability. (4) In general strata, the traditional support method is more economical and efficient, while in fault and fracture zones, steel tube support provides a safer working space and reduces the consumption of steel arches and shotcrete anchor support, demonstrating better economy and construction efficiency compared with traditional support methods.

Key words:  , Tianshan Shengli tunnel, open tunnel boring machine, fault and fracture zone, support method, surrounding rock stability, steeltube support